Not to pass up the opportunity to let you know about the chance of some precipitation in parts of the region on Friday night but a weak clipper type low will scoot east in the wake of tonight's arriving cool front, crossing to the south of Philadelphia on Friday night and early Saturday morning. Model trends keep this system, as of now, to the south of Philadelphia, likely to bring no precipitation to anyone north of a Dover-Avalon line. However, the Cape May and Delaware Beach contingent may have a few drops of rain or perhaps (not likely) a flurry on Friday night with this system.
All that said, this little wave doesn't look like it will get into Philadelphia -- the main upper flow aloft is generally keeping this puppy to our south.
Another clipper-type system will cross to our north on Saturday night, probably bringing flurries to the Poconos, perhaps Lehigh Valley. That system's calling card is simply to feed further energy into the southern wave as it organizes in the Atlantic into a storm system, plus draw in some additional cooler air that will help keep daytime highs on Sunday generally down in the lower half of the 40's.